Method of making ingots



P. C. RIPLEY IETHOD OF MAKING INGOTS Filed Jan. 27, 1930 Oct. 18, 1932.

Patented Oct. 18, 1932 warn-:oA STATES PATENT OFFICE PERRY C. RIPLEY, 0F CHICAGO, ILLINOIS, ASSIGNOR TO KESTER SOLDER COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS METHOD 0F MAKING INGOTS Application med January 27, 1930. Serial No. 423,898.

This invention relates to a process for forming uniform castings of metal alloys, and more particularly to a process for forming such castings from lead and tin alloys 1n which the ratio of lead to tin varies from the ratio of such metals in a true eutectic mixture. The invention further contemplates a casting so formed.

If lead and tin are fused together in the approximate ratio of three atomic weights of tin to one of lead and heat extracted from the solution, a point is reached where the solutlon solidifies en masse. This point is termed the eutectic point and the resulting solid the eutectic. Upon examination, it will be found that the solid is, in some respects, a chemical compound having the empirical formula BbSn,. According to many authorities, it is in realit a chemical compound.

This cad-tin solid has a lower melting point than any other solid solution of lead and tin and is the only sold solution-of lead and tin which is homogeneous; that is, the only alloy of these metals wherein the lead and tin are, in effect, combined as a chemical compound.

It, therefore, follows that any other alloy of lead and tin is composed of the eutectic of lead and tin together with free or uncombined lead or tin held in suspension in the eutectic. Thus, if a mixture of lead and tin containing these metals in other than the atomic proportions of one lead to three tin be fused and slowly cooled, lead or tin, depending upon which is in excess of the eutectic proportion, will recpitate until the eutectic mixture is reached, when the entire solution will freeze en masse. The resulting solid will contan the eutectic plus free lead or tin distributed non-uniformly throughout the solid. Since most commercial alloys of lead and tin are non-eutectic, it is apparent thatsuch alloys, in most instances, are of nonuniform composition, and, especially, is it generally true that large ingots or similar articles made therefrom are of non-uniform composition and, for that reason, objectionable where uniformity is a desired or a requisite property.

Sincefthe excess of thin Aor lead over the eutectic pro ortion precipitates during the gradual cooling of the fused alloy and tends to settle through the still liquid portions of the alloy mass, the slower the rate of cooling the greater the lack of uniformity in the composition of the resulting solid. If, on the other hand, it were possible to lower the temperature of the entire mass of fused lead and tin from its initial-solidifying point to the eutectic point practically instantaneously, the resulting eutectic would entrap the crystalsfof lead or tin in excess of the eutectic before they could fully precipitate or settle out, and, in that way, a substantially uniform alloy would result containing the lead and tin in the proportions throughout the solidified mass in which they existed in the fused mixture. A

While it is not only possible but also rather simple to obtain va rate of cooling approximating the above ideal in forming relatively small castings, it can be appreciated that in the formation of large castings a different problem is presented.

I have, however, devised a process wherein I can form relatively large castings of uniform composition from non-eutectic alloys of lead and tin; that is, alloys containing lead and tin in proportions other than those. in which they exist in the eutectic. In gen-V eral, my process consists in first pouring and rapidly coolin small diameter castings to form ingots o substantially uniform composition and then pouring further quantities of the lead-tin solution over and around a core formed of the relatively small ingots in a large jacketed mold, whereby such ingots extract heat from the solution in the central portion of the mold, the solution in the outer portions of the mold being cooled by external means, as by water or the like. In this way, a rapid freezing of the solution is obtained, the net result being a bonding together of the smaller ingots by the solution with the formation of a large ingot having a substantially uniform composition.

It is, accordingly, an object of this invention to provide a process for forming relatively large ingots of a uniform composition throughout from a non-eutectic alloy.

It is a further object of this invention to provide a process for rapidly extracting heat from a lead-tin solution bymeans of cores formed of small bodies of a uniform composition lead-tin alloy containing the lead and tin in the same proportions as exist in the lead-tin solution.

It is a further object of this invention to provide a relatively large casting of a non. eutectic lead-tin alloy havin a substantially uniform composition throug out its mass.

Other and further important objects will become apparent from the following descripthe small allo tion and appended claims.

My invention is best described in connection with the accompanying drawing in which a preferred embodiment of it is shown.

Figure 1 is a to view of the device showing several mol surrounded by cooling jackets.

Figure 2 is a section taken'along the line II-II of Figure 1 with certain parts shown in elevation.

Molds 1, 2, 3, 4, and 5 are located within a tank 6 which has a removable base 13. A cooling liquid circulates through the apparatus entering the tank 6 through pipe 7 and leaving it through pipe 8. Within the molds 1, 2, 3, and 4 are small alloy castings 10 surrounded by the molten metal 9. 'Figure 2 casting 10 is shown 1n elevation in mol s 1, 2, and 3 and in section in mold 4. Mold 5 contains a modification in which several small castings 11, are used. In Figure 2, two of these small castin s are shown in section and the center one 1n elevation.

The molds are preferably arranged on th arc of a circle II--II since this arrangement makes it convenient to pour the metal from a large ladle or pot which is supported from a central axis in such a manner that it ma be swung along this arc thereby bringing 1t into position over each mold for pourlng.

Accordin to my invention, I first fuse a mixture of ead and tin to form a solution containing these metals in the proportions desired in the finished casting. For instance,

in the formation of ingots to be used in dies for. making solder wire in which field this invention has great utility, lead and tin are' melted together to form a solution containing approximately 60% o f tin and 40% of lead by weight. Relatively small diameter'ingots are then formed from this solution by castingl in and uniformly distributed throughout the resulting ingots.

These ingots 10 are then removed from the molds, the removal being promoted by the ta er of the molds.

elatively large diameter ingots represented by both portions 9 and 10 having a weight say, 150 lbs. or more, are then produced by employing the small\ingots in the following manner A number of the relatively small diameter ingots 10 or 11 of uniform com osition are g'ouped at or near the central axis of a large 'ameter water-cooled mold 1, 2, 3, 4 or 5 of approximately the same height as said smaller diameter ingots. A further quantity of said lead-tin solution is then poured into the mold over and around said smaller ingots to completely fill the voids around and between the small ingots. The smaller ingots rapidly extract heat from the solution coming into contact therewith, whereb that portion of the solution is quickly soli ied, thus binding the smaller ingots together. Simultaneously, that part of the solution contacting the periphery of the mold is rapidly frozen by t e water or other mold cooling medium, so that the entire body of solution is converted into an homogeneous ingot. Because of the rapidity with which the heat is extracted from the solution, the resulting ingots will be of substantially uniform composition, the excess of lead over the eutectic being distributed throughout the' in ots.

The following comparative data o tained from ex eriments performed on 150-lb. ingots of ead-tin alloys, cast from solutions containing approximately 60% tin and 40% lead by wei ht, accordin to the conventional method and the metho of this invention, serve to indicate the great difference in the uniformity of the composition of the ingots resulting from the two processes. Three 150-lb. ingots were repared first by casting a molten mixture o 60% tin and 40% lea into molds and then three other 15G-lb. ingots were prepared b my process.

Each of the t ree ingots prepared by the conventional method was then extruded through dies in the form of wire solder. Upon analysis of the wire solder as the extru'sion progressed, the tin content showed a maximum variation in the case of one ingot of 5.24%, in another 3.53% and in the third 3.04%. The averael maximum variation in the composition of the three ingots throughout their respective masses wasz therefore, 3.97%.

The tin content of the wire extruded from the three ingots prepared in accordance with my invention was then progressively analyzed. In one ingot there was a maximum It can thus be appreciated that my method constitutes a decided improvement over the methods now in use in this art, since it permits the casting of relatively large ingots of substantially uniform composition. The use of larger ingots obviously makes for greater economies in production in permitting the use of larger capacity machines for extruding the metal alloys in the form of solder wire or the like. Further, the substantial uniformity of composition throughout the length of solder wire produced from the large ingots of my invention makes for uniform soldering results.

While, in the preferred method of carrying out my process, aplurality ofsmall diameter ingots are bonded together in forming a relatively large diameter ingot, it is to be understood that a single small diameter ingot may be employed to form an ingot of a slightly larger diameter, and this, in turn,

used to build up a still larger ingot, until anI ingot of desired size is obtained.

It should also be borne in mind that, while my disclosure particularly deals with the formation of ing-ots from an alloy containing as in said solution to thereby effect a rapid extraction of heat from that portion of the solution contacting said small ingots and a bonding to ether of said ingots and simultaneously eecting a conduction of heat from the remainder of the solution, whereby a rapid freezing of the entire mass of solution is obtained. v 3. As a new article of manufacture, a noneutectic tin-lead allo ingot having a diameter greater than two inches and having a substantially uniform composition throughout its mass, said uniform composition having a maximum variation of less than .74%.

In testmony whereof I have hereunto sub- -scribed my name at Chicago, CookpCounty,

Illinois.

" PERRY C. RIPLEY.

loo

by weight 60% tin and 40% lead, yet this is i not to be construed as a limitation, as castings l of uniform composition of other lead-tin alloys, as well as alloys of other metals, can be eicaciously made by my method.

Other changes may also be made in the method disclosed Without departing from the spirit of my invention and, accordingly, I do not propose to limit the invention claimed herein other than as necessitated by the prior art.

I claim as my invention:

l. The process of preparing a relatively large diameter ingot of substantially uniform composition throughout from an alloy contalnmg by Weight approximately 60% of tin and 40% of lead, which comprises casting a solution containing lead and tin in the ratio of 60% tin and/0% -lead about a core comprising a relatively small tin-lead alloy ingot having a diameter not greater than about two inches and being of uniform composition containing 60% of tin and 40% of lead whereby to effect a rapid extraction of heat from that portion of the solution contacting said small ingot and simultaneously effecting a conduction of heat from the remainder of the solution whereby a rapid freezing of the entire mass of solution iS obtained.

2. The process of preparing a relatively large diameter ingot of substantially uniform composition from a non-eutectic lead-tin alloy, which comprises casting a. solution4 containing lead and tin in a ratio other than that of relatively small lead-tin alloy ingots each having a diameter not greater than about two inches and being of uniform composition in yin the eutectic over and around a plurality,

which the lead and ti are in the same ratio. 

